Catalytic rearrangement of pinene to camphene



Patented Oct. 23, 1951 OATALHYTIC REARRAhLGEMENT ,oF To CAMPHENE Herrick B. Arnold, Wilmington, and James E. (Jarnahan, New Castle, Del., assignors to E. I. du'Pont de Nemours & Company, Wilmington, Del., a' corporation of ,iDelaware 7N0 Drawing. Application Augustz fi, 1.9 Serial No. 111 59.811

in t on relate to r rran ement 11??- fi-Qll @R 1 .19 p i fiqll l y 11 q i s w? r e rangement of pinene to camphene.

Camphene enters into the manufacture of many commercially imDQltant chemicals, notably camphor. Because of this, there is a continuous active interest low-cost, abundantly available, ;rearrangeab1e 'terpenes, such as the pinenes, for conversion to camphene Among talysts employed heretofore for effecting this rearrangement reaction are the earths, such-as Floridin; inorganic acids, such as titanic acids,:$ilicic acids, vanadicacids, molybdic acids; icomplex acids, such as silicotungstic acids, silicovanadic acids, aluminooxalic acids, etc.; acid salts, such as those of phosphotungstic acids acid magnesium phosphates, aluminum chloride, etc.; anhydrous silicate mineralsof the mica group n hqa vp rophyll et hese catalysts have not been entirely satisfactory L either because the yield of camphene has been too low, or because the time required for effecting the rearrangement in reasonable yield is longer than is desired for economic operation,

ormeeeus -emb r te f a io a vdistillation a always been required to isolate the product in mesl nate urit These h rtc m n op a e to ncreas e and en e to meet i v eb y the economics of :the Qperation.

It is an object of this invention to provide a novel method for the rearrangement of pinene t camph ne A- further.;,o ieet to evie e a novel catalytic 'cmethco .fo the earrangement of alphawinen to cam ene ,Azs l l the i e lisgto provide a method iiorzefieetin th rapid rearrangemen .alpha-nmen to nemnhenenfihi h purity, in; oo .yields- Oth r ebjects will appear hereinafter.

'.'.Ih.e .objects .orthisin ention ar aeeem lieh byLa LmethQd-lf-( therearran ment e iz n ll i camphene'whichc mprises nta tin t e in n with a m lybdite of a m a whee i e i are eli blez-in excess aqueou amm n aaee re in at this -,inve ntion pinene es e ia l a p aine is converted to camphene in high yieldsinashort time by h atin t e :P at reflux temperatore n-eonta t w h-e ely t of a m ta Wh s ion a e {not precipi t d a insolublexid or h droxi e hen so u i ns e ei salt :are tteatesiwi hzexee saaqueeu amnesia Inone embodiment of this invention a reactor fi te with a ref c nd e an st r "i charged with the alpha-pinene and molybdite ete1 .and h x ure is ea e t fefiuxena thus maintained until the freezin g point of the mixture is at least +12 C., which usually req i 5 9: 5 mi e 59 112 he treerm P931 ceases to rise with continued reflux. 'I h'e reaci en m ur weee filt e vane i the 9%???- ohen o pu ity reate ha i esi e i is subjected to fractienalldistillation to' collect the solid ortionbqilingat l 5l-l60 C. at a trnos phe i pressur The examples which follqware submitted to l us rat and n to mi thi n entieu- Q FQWZI Into a300 ml. round-bottomed l-necked flask equippedwith mechanical stirrer, an efficient reflux condenser, thermometer and nitrogen inlet tube-to provide an-inert atmosphere, was charged Crude Minutes at Oamphene 3%??? Reflux v gg Camghene P0. Per cent 4 8.4 v

.,.-E :aetiena d s illat on e th filtered smile 3 product after 64 minutes at reflux isolated camphene in 82% yield and conversion. The melting point was 47 C. Boiling points and melting points of the individual fractions which were cut during distillation of this product are tabulated below.

The catalyst used in the above example was prepared as follows:

Seventeen hundred sixty-six grams of ammonium paramolybdate [(NH4)6M07024 41-120], equivalent to 10 moles of M003, was dissolved in 5000 cc. of distilled water and neutralized by the addition of 900 cc. of 28% aqueous armnonia. The resulting solution of ammonium molybdate [(NH4)2M0O4] containing 1.9 moles excess ammonia was then added, with stirring, at room temperature to a solution of nickel nitrate, prepared by dissolving 2908 g. of nickel nitrate hexahydrate [Ni(NO3)2.6H2O], equivalent to 10 moles of nickel salt, in 5000 cc. of distilled water. A pale green precipitate was formed in an acid slurry having a pH of approximately 4.0 by alkaline-acid paper. The pH of the slurry was adjusted to 7.0 (Beckmann pH meter) by the addition of 500 cc. of 28% aqueous ammonia. The precipitate was then washed, filtered, dried, and calcined at 400 C. for 18 hours. The calcined product, by analysis, was found to contain 23.2% nickel and 46.4% molybdenum.

The calcined product, prepared as described above, was reduced in hydrogen, at gradually increasing temperatures up to 550 C. The reduced product was highly pyrophoric and glowed onexposure to air. Analysis of the reduced material showed it to contain 26.66% nickel and 53.1% molybdenum corresponding to NiMoO2.O.2MoO3 Example II Minutes {Conversion phene at Re- Memn Camflux Pointg phene 9. 4 Over 90% 10 9. 4 I 128 Over 90% 9. 8 10. 0 6. 8 3. 8

Example III In a third experiment using the methods and apparatus set forth in Example I but employing 11 g. of nickel molybdite catalyst which differed from the first two primarily in regard to its larger particle size, the following melting point data and infrared-determined camphene conversions were obtained at the indicated periods of reflux (155-158" C.).

Using the method and apparatus set forth in Example I, the following melting point data and infrared-determined campheneconversions were obtained in a run with cobalt molybdite catalyst at the indicated periods of reflux (154158 (3.).

Minutes if g Conversion at Rcfi to Camflux Pointg phene 4 Below 36 10 About -36 15 15- 0 25 10. 0 35 20. U 45 20. 2 75 21. 0

After 110 minutes at reflux the crude product was filtered and submitted to fractional distillation. In this way camphene in 91% yield and conversion and having a melting point of 49 C. was isolated.

Example V Example VI Using the apparatus set forth in Example I, 136 g. (1 mole) alpha-pinene was mixed with 10 g. of zinc molybdite catalyst and the mixture was stirred at reflux C.) under nitrogen for 2.5 hours. Infrared spectral analysis of the filtered crude product indicated a 25% conversion to camphene.

The catalysts used in the practice of this invention are the molybdites described and claimed in our copending application filed concurrently herewith, U. S. Ser. No. 111,982. Preferred molybdites, because of their especially high degree of activity, are the molybdites of nickel, cobalt, and copper.

The molybdites may be employed in the form of pellets or as finely divided powders, and they may be used as such or extended on inert supports such as alumina, silica, etc. The particular physical form of the catalyst for maximum activity depends upon the conditions under which the rearrangement reaction is to be effected. Thus, for vapor or liquid phase continuous operation it is best to have the catalyst in the form of pellets, thus minimizing mechanical losses. If the process, however, is to be operated as a batch operation, it is best that the catalyst be in finely divided form because in this way maximum catalytic activity is attained.

The amount of catalyst employed depends upon such interdependent variables as temperature, desired duration of contact, and general methods of operation; that is, whether the process is to be operated as a vapor or liquid phase continuous operation or batchwise. As a rule though, the amount of catalyst used is at least 0.01% by weight of the pinene treated. Amounts above 15% by weight of the pinene are not generally employed because no practical advantages accrue therefrom. In operating batchwise, the amount of catalyst normally employed would range between 5 and by weight of the pinene in order to obtain rapid but not uncontrollably vigorous reaction at reflux. In a continuous vapor or liquid phase process, the amount of catalyst normally employed would range between 0.01 and 5% by weight of the pinene.

The process is usually conducted in open reactors at atmospheric pressure. However, pressures below atmospheric can be used, particularly if it is desired to carry out the reaction under reflux at temperature below the atmospheric pressure boiling point of pinene to effect heat removal efficiently.

The temperature at which the rearrangement is effected depends upon the rate of reaction desired. Rapid reaction obtains at the normal boiling point of the system, but if desired, lower or higher temperatures of the order of 25 to 240 C. can be employed to obtain slower or faster reaction rates resulting respectively at the lower or higher temperatures. The reaction can be effected at room temperatures but periods of over one day are then required for completion, while at 155-160 C., periods of as low as 5 minutes give over 90% conversions.

The process of this invention is advantageous in yielding camphene of very high purity in high yields very rapidly. It has now been found that the molybdites described herein overcome the disadvantages characterizing prior catalysts for effecting the rearrangement of pinene to camphene.

Although the process has been described with particular reference to alpha-pinene, it is to be understood that other rearrangeable terpenes, such as beta-pinene, and such pinene-containing materials as gum terpentine, wood turpentine, and sulfate turpentine can be used in place thereof.

The conversion of alpha-pinene to camphene involves a multiple bond shift together with a rearrangement of the carbon skeleton. The process of this invention can also be used for effecting other types of molecular rearrangements. For example, by heating l-octene with cobalt molybdite at 200 0., under autogenous pressure for 3 hours, there is obtained in conversion a mixture of 2-, 3-, and 4-octenes, and by contacting ortho-xylene briefly with nickel molybdite, at 500 C., there is obtained a mixture of metaand para-xylenes.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claims.

We claim:

1. A method of converting a pinene to camphene which comprises contacting said pinene with a molybdite of a metal whose ions are soluble in excess aqueous ammonia.

2. A method of converting alpha-pinene to camphene which comprises contacting alphapinene with a molybdite of a metal whoseions are soluble in excess aqueous ammonia.

3. A method of converting a pinene to camphene which comprises heating said pinene at reflux temperature in contact with a molybdite of a metal whose ions are soluble in excess aqueous ammonia.

4. A method of converting alpha-pinene to camphene which comprises heating alpha-pinene at reflux temperature in contact with a molybdite of a metal whose ions are soluble in excess aqueous ammonia.

5. A method of converting a pinene to camphene which comprises heating said pinene in contact with zinc molybdite.

6. A method of converting a pinene to camphene which comprises heating said pinene in contact with nickel molybdite.

7. A method of converting a pinene to camphene which comprises heating said pinene in contact with cobalt molybdite.

8. A method of converting a pinene to camphene which comprises heating said pinene in contact with copper molybdite.

HERRICK R. ARNOLD. JAMES E. CARNAI-IAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 999,667 Montaland Aug. 1, 1911 1,967,430 Rebner July 24, 1934 1,985,792 Meerwein et al Dec. 25, 1934 2,382,397 Carson Aug. 14, 1945 

1. A METHOD OF CONVERTING A PINENE TO CAMPHENE WHICH COMPRISES CONTACTING SAID PINENE WITH A MOLYBDITE OF A METAL WHOSE IONS ARE SOLUBLE IN EXCESS AQUEOUS AMMONIA. 